The present invention relates to an installation for the propulsion or forward drive regulation in motor vehicles in the sense of a reduction of the undesired slippage of the driven vehicle wheels. A regulating circuit is coordinated to each driven wheel and responds to the slippage of this wheel in relation to the velocity of the non-driven wheel of the same vehicle side, which when exceeding a slippage threshold value by this wheel, effects a reduction and when dropping below this slippage threshold value, effects an increase of the output torque of the drive aggregate.
Such an installation is disclosed in the DE-PS No. 31 27 302. It includes a so-called "fast" regulating circuit which acts on the brake of a driven wheel if only this wheel tends to slip. It also includes a further regulating circuit which reduces the engine torque: when both driven wheels tend to slip, when one driven wheel tends to slip above a predetermined vehicle velocity, when driving through a curve, or when the vehicle longitudinal acceleration exceeds a predetermined limit value above a velocity in the starting range.
Propulsion or forward drive regulations with braking intervention are able to avoid larger regulating deviations owing to a rapid braking intervention, however, they are very cost-intensive as regards manufacture and operating safety because an undesired braking as a result of erroneous signals can lead to extraordinarily critical driving conditions.
In particular with propulsion or forward drive regulations which act exclusively on the engine torque, the coupled rotating masses of engine and drive connection become noticeable in a disadvantageous manner and lead to noticeable overshootings of the regulation, i.e., to an excessive slippage and great acceleration of the driven wheels. They are also a reason for a non-negligible time delay between an adjustment, for example, of the throttle valve in the carburetor of the engine and the engine reaction subsequently following the same.
It is therefore an object of this invention to so improve the propulsion or forward drive regulating installation exclusively the engine torque, i.e., to make the same more rapid, so that a brake regulating circuit can be dispensed with altogether.
The underlying problems are solved according to the present invention in that a further regulating circuit is coordinated to each driven wheel, which at least in the first regulating cycle or for a predetermined duration replaces the slippage regulating circuit. The further regulating circuit is so constructed that the output torque of the drive aggregate is reduced when the acceleration of the driven wheel exceeds the acceleration of the non-driven wheel of the same vehicle side by a predetermined amount, in that the difference between the wheel circumferential velocity of the driven wheel and that of the non-driven wheel of the same side which exists at the instant of the beginning of the torque reduction, is stored and is added to the wheel circumferential velocity of the non-driven wheel whereby this addition value forms a threshold value, and in that the output torque of the driving aggregate is again increased after the wheel circumferential velocity of the driven wheel drops below this threshold value. According thereto, the slippage tendency of a driven wheel is determined when the acceleration of this wheel exceeds the acceleration of the non-driven wheel of the same vehicle side by a predetermined amount. This can be detected much earlier than exceeding a slippage threshold selected from a technical regulating point of view owing to an earlier reduction of the engine torque a much smaller excess torque is transmitted to the wheel, respectively, the wheels. Consequently, the wheel can be caught more rapidly and drops below a threshold which is formed from the velocity of the non-driven wheel and the velocity difference between the driven and non-driven wheel which exists at the instant when exceeding the acceleration threshold, in general earlier than the slippage threshold which is set much higher. In this manner, a regulation with smaller overshootings and with fewer regulating cycles can be carried out so that a regulated brake intervention can be dispensed with altogether. This is also advantageous as regards the stability of the vehicle because a smaller driving slippage also entails smaller lateral guide force losses. According to a further feature of the present invention, this acceleration regulation will be carried out only, when the vehicle longitudinal acceleration lies below a predetermined value. However, if it lies above this value, it may be assumed that a dry gripping road is being travelled over so that a normal propulsion or forward drive regulation is permissive which can handle greater slippage values and does not reduce the acceleration of the vehicle.
In contrast thereto, the "acceleration regulation" can remain engaged beyond the normally provided duration as long as the vehicle cross acceleration b.sub.y is within a predetermined range, for example, 0.05 g&lt;b.sub.y &lt;0.15 g, in which a low frictional connection coefficient can be assumed. The signal representing the vehicle cross acceleration, however, can also be limited to a predetermined duration of, for example, 2 s. This suffices generally in order to stabilize the vehicle in the curve.